The present invention relates to a process for the hydroconversion of heavy hydrocarbon feedstocks and, more particularly, a three-stage process employing upstream flow reactors with catalysts in the first and third stages.
Processes for the thermal and catalytic hydroconversion of hydrocarbon feeds are well known. The term hydroconversion as used herein means the conversion of residues, asphaltenes and resins remaining from atmospheric or vacuum distillation of conventional and/or non-conventional crude oils into lesser boiling point distillated products. When treating residues which have a disproportionate amount of contaminant elements such as vanadium, nickel, nitrogen and sulfur, catalysts are often employed in the hydroconversion process. These catalysts, which are generally very expensive, have a relatively short life when treating such residues.
U.S. Pat. No. 4,434,045 to Vernon et al. discloses a process for hydrocracking residuals in the presence of a hydrogen donor solvent. U.S. Pat. No. 4,447,313 to Gorring et al. relates to a process for hydrocracking residuals wherein a deasphalting stage precedes the hydrocracking stage so that most of the heavy fractions containing the majority of the contaminants are removed thereby leaving a considerable amount of residual without conversion. U.S. Pat. No. 4,431,526 to Simpson et al. is drawn to a process for the hydrotreatment of hydrocarbons particularly for the hydrodesulfurization and hydrodemetallization wherein the process is performed in two steps using average sized catalysts of different pore size. Finally, U.S. Pat. No. 4,431,525 to Hensley, Jr. et al. teaches a process for the hydrotreatment of hydrocarbon streams containing metals, asphaltenes, nitrogen compounds and sulfur wherein the process comprises three different steps, each step employing a catalyst having different physical and chemical properties. While the foregoing U.S. patents discuss the problems faced when treating heavy hydrocarbon feeds, none of the processes teach the specific process of the present invention employing the specific equipment as set forth in the present invention. Generally the prior art processes fail to extend the life of the catalysts to any significant amount.
Naturally it would be highly desirable to develop a process for the hydroconversion of heavy hydrocarbon feedstocks into usable distillates while at the same time improving the life of the catalysts employed in the process.
Accordingly, it is a principal object of the present invention to develop a process for the conversion of heavy hydrocarbon feedstocks characterized by high molecular weight, low reactivity and high metal contents.
It is a particular object of the present invention to provide a multi-step process for the conversion of heavy feedstocks wherein upstream flow reactors with catalysts are employed in the first and third stages.
It is a particular object of the present invention to provide a process as aforesaid wherein the intermediate stage between the first and third stages comprises a down flow thermal cracking step.
It is a still further object of the present invention to provide a process as aforesaid wherein the catalyst employed in the first stage of the process is capable of demetallizing organometallic complexes of high molecular weight and cracking resistance and a catalyst in the third stage which is capable of cracking molecules of high cracking resistance.
Further objects and advantages of the present invention will appear hereinbelow.